At the present time, vehicle door handles are equipped with devices for detecting a user's presence. The detection of a user's presence, combined with the recognition of a “hands-free” remote access control badge worn by the user, enables the openable body sections of the vehicle to be locked and unlocked remotely. Thus, when the user wearing the corresponding electronic badge identified by the vehicle wishes to unlock the vehicle, he approaches or touches the vehicle door handle and the openable body sections of the vehicle are then automatically unlocked. When the user approaches or presses on a precise location on the vehicle door handle, called the “unlocking area”, the door (or alternatively all the openable body sections) is/are unlocked without any further action by the user. Conversely, when the user, still wearing the necessary badge and identified by the vehicle, wishes to lock his vehicle, he closes the door of his vehicle and approaches or momentarily presses another precise location on the handle, called the “locking area”. By means of this gesture, the openable body sections of the vehicle are automatically locked.
These presence detection devices usually comprise two capacitive sensors, in the form of two electrodes connected electrically to a printed circuit and integrated into the door handle, each in a precise locking or unlocking area. Usually, one electrode is dedicated to each area; that is to say, one electrode is dedicated to the detection of the user's approach and/or the contact of his hand in the locking area, and one electrode is dedicated to the user's approach and/or the contact of his hand in the unlocking area.
The presence detection device further comprises a radio frequency antenna, usually of the LF (English abbreviation for “Low Frequency”) type. The detection device is connected to the computer of the vehicle or ECU (English abbreviation for “Electronic Control Unit”), and sends it a presence detection signal. The vehicle's computer has previously identified the user as being authorized to access the vehicle; alternatively, it proceeds to perform this identification after receiving this presence detection signal. For this purpose, it sends an identification request via the radio frequency antenna to the badge (or the remote control) worn by the user. This badge responds by sending its identification code by RF (radio frequency) radiation to the vehicle computer. If the computer recognizes the identification code as the code that authorizes access to the vehicle, it triggers the locking/unlocking of the door (or of all the openable body sections). However, if the computer has not received an identification code, or if the received identification is erroneous, the locking or unlocking does not take place.
These vehicles are therefore equipped with door handles comprising a detection device which itself comprises a radio frequency antenna, usually operating at low frequency, and two electrodes connected to a microcontroller integrated into a printed circuit and supplied with a voltage.
Purely for explanatory purposes, the device considered here is a detection device D comprising two electrodes, one electrode being dedicated to the unlocking area while the other electrode is dedicated to the locking area, said two electrodes being connected to a printed circuit comprising a microcontroller and an LF antenna. A prior art detection device D is described with reference to FIG. 1.
FIG. 1 shows a door handle 10 of a motor vehicle (vehicle not shown) in which a device D for detecting a user's presence is located. Said door handle 10 comprises a first surface S1 oriented toward the door P and a second surface S2, opposed to the first surface S1 and therefore oriented toward the side opposite the vehicle, or more precisely toward the user (not shown). This detection device D comprises a first unlocking electrode E2, having one face located near the first outer surface S1, control means 60 and an LF antenna (not shown) having one face located near the second outer surface S2, a second, locking, electrode E1 having one face located near the second outer surface S2, and control means 60. The first and second electrodes E1, E2 are connected to the control means 60. These control means 60 measure the capacitance at the terminals of each first and second electrode E1, E2 in order to detect the presence (approach and/or contact) of a user in the detection areas, that is to say in a locking area Z1 or in an unlocking area Z2, and consist, for example, of a microcontroller 60 integrated into a printed circuit 80. The LF antenna (not shown), for its part, is connected to an on-board computer of the vehicle (not shown) of the “Body Controller Module” (BCM) type, which manages the identification requests sent by said LF antenna.
However, this prior art detection device D has serious drawbacks.
In fact, the detection of a user's approach by means of capacitive sensors (the first and second electrode, E1 and E2) is not robust, and generates false positives.
In particular, in some environmental conditions, when the ambient air is humid, or if salt is present on the roads, a capacitive coupling is created between the detection areas (the locking area Z1 and the unlocking area Z2) and the metal parts of the vehicle, preventing any detection of a user's presence by the capacitive sensors.
Moreover, raindrops or snowflakes on the door handle increase the value of the capacitance measured by the capacitive sensors, thus giving rise to false positives.
Finally, detection by capacitive sensors is incompatible with handles coated with metallic paint or having chromium-plated surfaces, since the presence of metal in the handle creates a coupling with the detection areas and disables the user's presence detection.
While false positives are undesirable for some vehicles, they are completely unacceptable for other vehicles.
This is the case with vehicles fitted with deploying handles, that is to say handles in which the detection of a user's presence causes the movement of a motorized handle, which is fully integrated into the door when at rest, and is deployed and projects from the door when activated. For this type of handle, the deployment or retraction of the handle at the incorrect time, due to a false positive of the capacitive sensors, may trap the user's hand.
This is also the case in vehicles having electrically assisted opening, for which the unlocking detection is accompanied by not only the unlocking, but also the opening, of the door. In this case, false positives cause the door to open at the incorrect time.
Finally, false positives are unacceptable for vehicles having the “Safe Lock” safety function, where the locking detection causes the vehicle to be locked not only from the outside but also from the inside (anti-theft device). In this case, false positives may cause the user to be trapped inside the vehicle.
To overcome these drawbacks, there is a known prior art method of replacing at least one of the capacitive sensors, for example the capacitive sensor dedicated to locking the vehicle, with a mechanical switch of the push button type; however, a button on a handle is unsatisfactory for users in terms of aesthetic appearance and ease of use. For example, the button is visible from the outside, and is not suitable for deploying handles, where discretion regarding the presence of the handle in the door is desired above all else.
Moreover, pressing a push button is less convenient for the user than the automatic detection of the approach of his hand toward a handle which requires no pressure.